Method of preparing pretreated mineral aggregate minerals



Dec. 22, 1942. c. c PLUMB 2,305,989

METHOD OF PREPARING FEE-TREATED MINERAL AGGREGATE MINERALS Filed Oct. 18, 1939 TRNK muck R CRR I! W 4; -conns5 qRAVEL I INVENTUR.

Ja/X 63 Plzxw aw/4w A TTURNEYS.

//MEDIUM GRHUEI; (-SAND ETC 7 OTHERPOR s MATERIA Patented Dec. 22, 1942 UNETE ST METHOD OF PREPARING PRETREATED MINERAL AGGREGATE IHINERALS Charles C. Plumb, Providence, R. I.

Application October 18, 1939, Serial No. 299,928

2 Claims.

This invention relates to a process ormethod for treating large deposits of mineral aggregate with a liquid binding agent, and. is directed more particularly to the pre-treatment of large deposits of gravel, sand or stone, either in the form of a natural bank or bed, or in a storage pile, with liquid bitumen, such as, for example, oil asphaltic materials or the natural asphalts, tar products and emulsions of the same or of equivalent bituminous materials for subsequent use as a road surfacing material and for other purposes.

In the preparation of mineral aggregate, such as gravel, sand, or crushed stone combined with a bituminous binding agent for use as a paving or asa road surfacing material, and for other similar purposes, there are three common methods now generally employed at the present time for making premixed bituminous concrete, the first of which consists in premixing in a plant by means of a power mixing apparatus the mineral aggregate and the liquid bittunen, particularly the petroliferous substances such as the so-called oil asphalts or tars, in which pug mills or other mechanical mixing apparatus are employed for combining and producing uniform homogeneous mixtures of the ingredients. Another method commonly used is that of hand mixing the components of the combined product in which truck loads of gravel, sand, or loose stone are conveyed from the gravel pits or banks to various road building projects at locations re mote from the ground banks and thereafter are manually mixed with the liquid asphaltic or tar binding agent by laborers with shovels.

Another known method is that disclosed in the patent to Durfee, No. 2,043,037, of June 2, 1936, in which the mineral aggregate is pretreated by a method which consists in periodically depositing, as by mechanical conveying appaand the requirement of the use of expensive mixing equipment, thereby rendering the purchase cost of the premixed product for large scale road construction out of reach of the funds available to small towns and rural communities for their road building projects.

V The hand method or the second of the premixed processes above-named also is found to be expensive owing to its slowness, due to the manual labor required to perform the process, and it does not result in the production of a uniform product.

The third or the patented Durfee process also is expensive, since it requires that the material be mechanically excavated by a power shovel from the bani; and dumped in measured quantities at another location to form a pile, which additional handling of the material, along with the subsequent spraying of the binding agent on the pile after each separate discharge thereon considerably increases the selling cost of the combined product. Furthermore, the piles of the stratified treated material cannot be kept for an indefinite and prolonged period exposed to the weather, if storage of the combined materials I 'after treatment is attempted, such as through the winter, since the piles gather moisture and freeze so that when thawed in the spring, they will have a high moisture content which is detrimental to road construction. Durfees combined product must therefore be mixed in measured quantities for use at once, and cannot be stored with efficiency for too long a period for future use and distribution.

It is therefore the primary object of this invention to overcome the objectionable features found in the various prior art methods or processes above described and to provide a simple and economical method or process for preparing pretreated mineral aggregate which may be practiced without disturbing the natural condition of the bank or bed of the aggregate and to be drawn on for distribution at any future period.

Another object of the invention is to provide a method or process for treating mineral aggre-, gate in its natural location which will eliminate exposure of the aggregate and the treated materials to the weather until such time that the combined product is to be used.

Another object of the invention is to provide a method or process for preparing mineral aggregate which will eliminate the necessity of'disturbing the natural condition of a bank of mineral aggregate, such as gravel or sand, until the same is to be removed for use or distribution, and yet provide a product combined with a liquid binder which is incorporated in the same and permeates throughout the aggregate to coat the same and be suitable for the purposes indicated.

Another object of the invention is to provide 55 a method or process for preparing mineral ggregate for the purposes indicated by treating it,

in its natural airtight-sealed state in the large bank or bed where it occurs without disturbing the natural state of the material, by-impregnatw ing a porous portion of the bank containing the aggregate with liquid bitumen whereby theincorporated bituminous material may permeate throughout the aggregate and be distributed thereover to coat the same and yet be available in its applied liquid condition combined with the aggregate for subsequent distribution and use when the bank is opened.

Another object of this inventionis to provide an improved method or process for treating mineral aggregate by treating it in a bank or bed with a liquid binding agentwhereby the combined product may be stored without solidification or loss of the binder for distribution and use at a future period.

Another object of the invention is to provide a method or process of the above type for treating mineral aggregate in whichthe control of the proportion of the liquid binding agent with respect to the mineral aggregate onwhich it is applied when the treatedvaggregate is removed from the bank is by the observation of the depth of penetration of the binding agent through. the porous layer of aggregate by the shovel operator who determines the depth of digging of the bank and the quantity of lean or untreated material to be scooped up with reference to the treated material during shovelling to secure the required proportions of the components .in the treated product excavated from the bank.

With these and other objects in view, the invention consists of certain novel features of construction, as will be more fully described, and particularly pointed out in the appended claims.

In the accompanying drawing:

Fig. l is a cross sectional view representing a typical gravel bank in its natural state showing the various strata of gravel, sand and other materials and depicting the impregnation of the bank with a liquid binding material supplied under pressure from a tank truck located at the top of the bank.

Fig. 2 is a cross sectional view through an opened gravel bank or pit in which treatment of the gravel is effected from a distributing pipe.

introduced into the open face of the bankand supplied with a liquid binding agent forced under pressure from a tank located at the loading level or floor of the pit;

Fig. 3 is a cross sectional view of the bank illustrating a relative position of the shovel with respect to the open side of a gravel bank whereby the scoop action of the shovel will insure a required content of theh'quid binding agent in the resultant mixture of the untreated and the treated gravel in each bucketful scooped up;

Fig. 4 is a plan view of a gravel bank illustrating diagrammatic-ally the impregnation of the same with the liquid bindingmaterial as supplied under ressure'from a'tank. car, and also way construction and maintenance.

showing an arrangement of treating pipes whereby various contiguous areas of the bank may be treated;

Fig. 5 is a perspective view showing the treatment of a loose storage pile of aggregate in accordance with the invention;

Fig. 6 is a view showing the process as being performed by trenching the surface of a bank to be treated; and

Fig. 7 is a fragmentary view of a treating pipe.

Most communities, such as counties, cities and towns, allocate certain funds annually for high- It is the I duty of the officials in charge of streets and highlocally, thereby reducing expensive haulage and freight charges to a minimum. There are very few, if any, small cities and towns who can afford to purchase the present type of premixed materials. due to the high cost of manufacture at the mixing plant, plus the hauling charges from there to the. communities where they are to be used. On the other hand, most communities generally ownor .have available numerous large natural gravel and sand deposits in the form of banks or beds situated at various locations in the vicinity of roads being built or repaired.

Hence, any method or process that could be employed for the treatment of these local gravel banks in their natural state with a binding agent, particularly liquid bitumen, so as to make available to these communities a low cost bituminous concrete for use in their roadbuilding program, or as a patching. material would result in such a considerable reduction in the cost of manufacture of a road-building material utilizing such deposits of mineral aggregate of a local source as to make available to such small outlying communities substantial funds for additional maintenance and expansion of their road construction program, which monies otherwise would be exhausted and such expansion impossible under present-known expensive premixed methods of manufacture for making pretreated mineral aggregate combined with a binding agent.

Thepresent invention is therefore directed to the preparation and the pretreatment of large deposits of mineral aggregate material suitable for paving and road surfacing purposes, such as gravel and sand, in their natural state and location in which they are found to occur at the source of supply, and also to the pretreatment of large storage piles of such aggregate materials or of loose stone, by discharging into and impregnating these deposits with a liquid binding agent, preferably liquid bitumen, to provide. a treated product suitable for subsequent use in road building construction and for other. purposes.

The liquid binding agent to be employed preferably consists of liquid bitumen, preferably such petroliferous substances of the so-called oil tars and asphalts, or emulsions of the same or various common types of bituminous materials usually employed in highway or paving constructions. The viscosity of the binding material used preferably should be of a fiowable consistency under pressure, and it may comprise any of the cut back asphaltic or tar materials. By the term cut-back" is meant those asphalts or tar products that are admixed with naphtha or other volatile solvents insufficient quantity to render them flowable at a moderately low temperature.

The bituminous or asphaltic material may be.

derived from tar or asphalt, or emulsions of the same.

It-is' a well-known fact that gravel banks vary greatly in the nature of materials present and their relative gradation, so that the exact nature of these are first determined by local and resident officials or engineers prior to any treatment of the bank in accordance with the method or process of the present invention in order that they may recommend and specify the location of treatment points and the particular mode of practicing the method or process of the present invention. Accordingly, a stud of the location, condition and general geological structure of the bank, bed or pit where the gravel or sand is found is made preliminary to treatment of the same with liquid bitumen during which investigation a determination of the type of gravel, quantity, location of the deposit, and the apparent porosity of the bank is made in a suitable manner, such as, for example, by test borings into various portions of the bank.

Treatment of the bank may be begun in accordance with the method or process of the present invention and at treating points specified according to the recommendations and specifications of the oificials or engineers based upon their analysis and study of the above data.

With reference to the drawing, Fig. 1 illustrates one method of carrying out the invention wherein there is shown a treating pipe I sunk into the upper portion of a gravel bank, the treating pipe being of sufficient length that its lower end will terminate at a depth below the top surface of the bank where there is found to be a porous portion [2 of good, clean, coarse gravel of first quality. A liquid binding agent, such as liquid bitumen, preferably an oil asphalt or tar product, is then supplied from a tank truck l3, of predetermined capacity and forced under pressure by means of pump M on the truck [3 through a pipe line or hose I5 connected suitably with the top end of the treating pipe III to deliver the binder thereto and discharge it from the inner end of the treating pipe into the interior of the bank so as to impregnate the porous gravel portion to be treated with a predetermined quantity of the binding material, The expelled liquid will be forced through the porous portion I 2 of gravel to permeate through the same and flow downwardly through the succeeding under layers of gravel and sand l6 and IT to coat the materials thereof. After impregnation of the bank with the binding agent, the treating pipe I0 may be removed from the bank and the opening in the top soil I8 left by the pipe [0 may be sealed in any suitable manner, such as by means of a plug of soil or loam. It will therefore be seen that the natural arrangement of the gravel deposits has not been disturbed by the treating process above described, and since the layer of top soil or loam forms a natural air-tight seal for the bank, then no air can enter the bank to remove any volatile solvent agent that might be incorporated with the asphalt or tar, such as naphtha, to cut back the same and modify the viscosity to the asphaltic or tar materials. Hence, the liquid binding agent will be retained in a liquid state during storage of the treated aggregate and until such future time when the bank is opened up for distribution and use of the treated material.

It is well-known in engineering practice that satisfactory bituminous concrete mixes utilizing gravel aggregate should contain at least from six to eighth per cent bitumen content. Therefore, in the practice of the process or method of the present invention which covers impregnation of natural deposits of gravel with liquid bitumen, it will be quite evident that the bitumen content of portions of such deposits after treatment will contain an excess of bitumen content. Therefore, in order to obtain a treated aggregate prod-' not containing from at least six to eight per cent of bitumen this control will be effected by the local engineer in charge on location at the time of opening up of the gravel or sand bank and he willdetermine the depth of penetration in the bank by'the liquid binding agent and the percentage of the same, such as the liquid bitumen, present in the impregnated portion, and then specify the depth of digging into the bank so as to mix sufiicient untreated material with the treated material in order tomaintain the required proportions of aggregate and binder in the mixture being excavated or being scooped up from the bank. Where the upper layers of the deposits appear to contain an excess amount of bitumen, the determination is then made as to the proper depth of material to be handled by the power shovel to produce a resultant mixture of aggregate and binder having an asphalt or tar content of the proportions required.

Ihus, in Fig. 3, the bucket 22 of the steam shovel 23, shown on the loading floor of the bank for loading a truck 24, scoops up in each bucketful a quantity of untreated aggregate from a lower portion of the bank to incorporate this with the treated aggregate in the upper portions of the bank, as indicated at 22' by the dotted position of the bucket, containing the high bitumen content in order to obtain the required proportion of binder and aggregate in each bucketful of mixture being shovelled from the bank. If desired, the shovel operator may break down the face of the bank with the bucket of the shovel and turn the treated material over with the bucket until it has been sufliciently incorporated with the untreated material.

If difficulty is encountered in securing the proper penetration of the liquid binding agent into the bank when the impregnating procedure is begun, then'an increased penetration action may be secured in the bank by increasing the capillarity of the portion thereof to be treated. Thus, it may be found in some location that the deposits of the aggregate are not very porous and exhibit poor permeability so that it will be necessary to prime the deposit in question with a wetting agent, such as a light mineral oil, to

increase the covering power of the liquid binding agent. The mineral oil may be incorporated into the bank through the treating pipe Ill prior to the introduction of the liquid binding agent into the bank.

In case the natural deposits of the mineral aggregate are found to be very dense or tightly compacted to such a condition as to not absorb the liquid binding agent or to render difficult the driving into the bank of the treating pipe to a depth necessary for proper treatment of the gravel deposit, then a slight charge of an explosive may be set off at suii'icient depth in the bank in order to shake the gravel loose and open up crevices prior to the application of the liquid treating material or the liquid binding agent.

In Fig. 1 there is also shown a second treating pipe to which is delivered through the pipe line or hose 2| from the pump M of the tank truck a predetermined quantity of the liquid binding agent under pressure for incorporation into another areaof the porous layer I2 whereby one or more discharges of the liquid binding material may be made at one time from the tank truck I3. It will be obvious to those skilled in the art that suitable pressure relief valves may be incorporated in the respective pipe lines connecting the treating pipes l and with the tank truck in order to take care of any back pressure that might occur in forcing the liquid binding agent into the bank.

As illustrated in Fig. 2, there is shown a slightly modified form of the invention in which treatment of the bank is made from an open face or side after the bank has been opened for removal of the material. In this view, the treating pipe is driven from a sidewise direction into the open side of a porous portion 26 of gravel, and theliquid bitumen or other liquid binding agent, after being discharged from the inner end portion 21 of the pipe 25, will permeate through the material :in the vicinity of the discharge and flow downwardly through the successively lower porous portions of the bankbeneath the sphere of action of the discharge in order to permeate the same and thoroughly coat the material thereof. The treating liquid is supplied from a tank truck 28 located at the loading level or floor of the gravel bank or pit, and the liquid binding agent is delivered under pressure to the treating pipe 25 through the pipe line or hose 29 by means of the pump 30, on the truck. The treating pipes I0, 20 and 25 may be made of suitable metal, such as galvanized steel, having perforated side walls as indicated at 4! in Fig. 7 with a drive point 42 closing its lower end opening.

Fig. 4 illustrates a plan view of an area of a gravel bank to be treated in which there is shown an arrangement consisting of a treating pipe 3| driven into the top portion of the bank for treating a generally central area thereof, and auxiliary treatment pipes 32, 33, 34 and 35 located for treating areas of the bank outside the range of action of the treating pipe 3|. It will be obvious that these auxiliary treatment points are subject to variation according to location and number, dependent upon the local conditions, requirements and the nature of the ground deposits to be treated. In this view, the liquid binding agent is depicted as being supplied from a railroad tank car 36 which is movable along atrack 31 adjacent the gravel deposit for supplying the liquid binding agent, such as liquid bitumen, under pressure by means of a pump 38 and through pipe lines 39 and 40 to the treating pipe 5."

3|. It will also be obvious that the auxiliary treatment points 32, 33, 34 and 35 will beaccessible to the delivery of the treating material from the tank car 36 as the position of the same is moved along the railroad track in order to bring the car within easy reach of such auxiliary treatment points.

In Fig. 5 there is shown another method of practicing the invention in which a pile of loose mineral aggregate, such as a storage pile of gravel, sand or stone is impregnated at various portionsthereof by means of treating pipes 5| and 52 thrust into the pile at various pointsfor discharging a predetermined quantity r of liquid binding agent, into the pile and supplied under pressure to the treating pipes from a tank car or tank truck. I

Fig. 6 of the-drawing illustrates another feasible method for practicing the invention and consists in trenching the surface containing the aggregate of the bank 55 deposit to be treated as indicated at 55 andthen filling the trench with the liquid binding agent 51 and allowing it to soak into the bank and permeate through the gravel or aggregate deposit in its downward movement to coat the same without the use of applied pressure on the impregnating liquid.

Having thus described several illustrative embodiments of my invention and the best mode known to me for carrying out my method,-I desire it to be understood 'that although specific terms are employed, they are used in a generic and descriptive sense and not for the purpose of limitation, the scope of the invention being defined and limited only by the terms of the appended claims.

I claim:

1. The process of preparing pre-treated mineral material for subsequent use in paving and other purposes, which consists in injecting into a deposit of mineral aggregate in its natural deposit state and at a point removed from the surface, a liquid bitumen binder in suflicient quantities to permeate a substantial area of said'deposit about the point of injection of said bitumen binder therein, subsequently removing in quantities as may be required from said deposit amounts of both the impregnated and non-impregnated material in such quantities ofeach so as .to have in the finished material a predetermined proportion of binder to mineral material and then mixing the removed impregnated and non-impregnated materials'so as to uniformly distribute the binder.

2. The process of preparing pre-treated mineral material for subsequent use in paving and other purposes which consists in injecting a liquid bitumen binder previously mixed with a volatile solvent to render the bitumen fiowable at a moderately low temperature, in a natural mineral deposit and in sufiicient quantities to impregnate a substantial portion of the area of the deposit being treated and at a point sufficiently removed from the surface thereof to seal the bitumen therein to prevent the escape of the volatile solvent agent admixed therewith to retain the bitumen in a flowable condition, subsequently removing in' quantities as may be required material from such treated deposit to a depth in said deposit to include in the removed material both.'impregnated andnon-impregnated material in such amounts of each so as to'have in thefinished material a predetermined proportion of binder to mineral aggregate and then mixing such removed material so as to uniformly dis tribute the binder.

' CHARLES C. PLUMB. 

